Recently accumulated experimental evidence for aurophilic interactions in and between molecular gold(I) compounds and the results of pertinent theoretical calculations are reviewed for the period from 2007 to mid-2011. The influence of the intra- and intermolecular bonding contacts between the closed-shell metal centres, Au–Au, on the molecular and crystal structures, and the consequences of these effects for the chemical and physical properties of gold compounds are summarized for the various classes of mono- and polynuclear systems. The literature survey builds on the contents of previous reviews and relates new experimental and theoretical findings to earlier observations (353 references).

Aurophilic interactions as a subject of current research: an up-date

On the basis of Kohn–Sham density functional (DFT) investigations on elementary organic and organometallic reactions, we show how a detailed understanding of the electronic structure of a reaction system can help recognize certain characteristics of the process, yielding valuable mechanistic concepts. The concept of the base as a selective catalyst in E2 eliminations, for example, leads to a straightforward explanation for the general preference for anti over syn stereochemistry in base-induced elimination reactions. Furthermore, electronic structure considerations provide the so-called E2–SN2 mechanistic spectrum, in terms of which one can interpret and understand the competition between elimination and substitution reactions and the shift, on solvation, of the reactivity from E2 to SN2. In addition, mechanistic concepts from organometallic and organic chemistry are linked as we argue that oxidative addition may be conceived, in some respect, as the organometallic analog of the frontside SN2 substitution. Finally, we introduce the ideas of “activation strain” of and “transition state interaction” between the deformed reactants in the activated complex, which together determine the activation energy, ΔE*=ΔE+ΔE. They prove to be helpful conceptual tools for understanding in detail how activation barriers and relative efficiencies of competing reaction mechanisms arise and how they may be affected (e.g., by changing reactants or by solvation). © 1999 John Wiley & Sons, Inc. J Comput Chem 20: 114–128, 1999

Understanding reactivity with Kohn–Sham molecular orbital theory: E2–SN2 mechanistic spectrum and other concepts

Weak attractive interactions between closed shell metal ions have been increasingly studied in the last few years and are generally designated as metallophilic interactions. They are best evidenced in the solid state where structural data obtained by X-ray diffraction provide precise information about the distance between the metals involved. The strength of such metal–metal interactions has been compared to that of hydrogen bonding (ca. 7–11 kcal mol−1) and is clearly sufficient to bring about novel bonding and structural features and confer interesting physical properties such as luminescence, polychromism, magnetism or one-dimensional electrical conductivity. The Cu(I)–Cu(I), Ag(I)–Ag(I) and Au(I)–Au(I) interactions have been increasingly observed and the latter have certainly been the most studied. Early qualitative analyses of the aurophilic attraction focused on Au–Au bonding originating from 6s, 6p and 5d orbital mixing. Numerous theoretical studies on metallophilic interactions continue to be carried out at various levels of sophistication which take into account relativistic and correlation effects to describe these van der Waals-type interactions. In this critical review, we would like to focus on the synthesis and structures of heterometallic clusters of the transition metals in which intra- rather than intermolecular d10–d10 interactions are at work, in order to limit the role of packing effects. We wish to provide the reader with a comparative overview of the metal core structures resulting from or favoring metallophilic interactions but do not intend to provide a comprehensive coverage of the literature. We will first examine heterometallic clusters displaying homometallic and then heterometallic d10–d10 interactions. Although the focus of this review is on d10–d10 interactions involving metals from the group 11, we shall also briefly examine for comparison some complexes displaying intramolecular d10–d10 interactions involving metals from other groups (188 references).

/pdf/intramolecular-d10-d10-interactions-in-heterometallic-581tky0doc.pdf

Intramolecular d10–d10 interactions in heterometallic clusters of the transition metals

Metal-mediated and metal-catalyzed reactions of isocyanides.

Reductive elimination from partially or completely oxidized metal centers is a vital step in a myriad of carbon-carbon and carbon-heteroatom bond-forming reactions. One strategy for promoting otherwise challenging reductive elimination reactions is to oxidize the metal center using a two-electron oxidant (that is, from M((n)) to M((n+2))). However, many of the commonly used oxidants for this type of transformation contain oxygen, nitrogen, or halogen moieties that are subsequently capable of participating in reductive elimination, thus leading to a mixture of products. In this Minireview, we examine the use of bystanding F(+) oxidants for addressing this widespread problem in organometallic chemistry and describe recent applications in Pd(II) /Pd(IV) and Au(I) /Au(III) catalysis. We then briefly discuss a rare example in which one-electron oxidants have been shown to promote selective reductive elimination in palladium(II)-catalyzed C-H functionalization, which we view as a promising future direction in the field.

/pdf/bystanding-f-oxidants-enable-selective-reductive-elimination-5978o2s8wz.pdf

Bystanding F+ oxidants enable selective reductive elimination from high-valent metal centers in catalysis.

Dimolybdenum and Ditungsten Cyclopentadienyl Carbonyls with Electron-Rich Phosphido Bridges. Synthesis of the Hydrido Phosphido Complexes [M2Cp2(μ-H)(μ-PRR‘)(CO)4] and Unsaturated Bis(phosphido) Complexes [M2Cp2(μ-PR2)(μ-PR‘R‘ ‘)(CO)x] (x = 1, 2; R, R‘, R‘ ‘ = Et, Cy, tBu)

Structure and Bonding in the Unsaturated Hydride- and Hydrocarbyl-Bridged Complexes [Mo2(η5-C5H5)2(μ-X)(μ-PCy2)(CO)2] (X = H, CH3, CH2Ph, Ph). Evidence for the Presence of α-Agostic and π-Bonding Interactions†

M. Esther García

Papers

Dimolybdenum and Ditungsten Cyclopentadienyl Carbonyls with Electron-Rich Phosphido Bridges. Synthesis of the Hydrido Phosphido Complexes [M2Cp2(μ-H)(μ-PRR‘)(CO)4] and Unsaturated Bis(phosphido) Complexes [M2Cp2(μ-PR2)(μ-PR‘R‘ ‘)(CO)x] (x = 1, 2; R, R‘, R‘ ‘ = Et, Cy, tBu)

Structure and Bonding in the Unsaturated Hydride- and Hydrocarbyl-Bridged Complexes [Mo2(η5-C5H5)2(μ-X)(μ-PCy2)(CO)2] (X = H, CH3, CH2Ph, Ph). Evidence for the Presence of α-Agostic and π-Bonding Interactions†

Phosphinidene-bridged binuclear complexes

Formation and Cleavage of P-C, Mo-C, and C-H Bonds Involving Arylphosphinidene and Cyclopentadienyl Ligands at Dimolybdenum Centers

A Versatile and Unprecedented Triply Bonded Dimolybdenum Carbonyl Anion